• Journal of Magnetics
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• v.13 no.3
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• pp.106-109
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• 2008

Almost monodisperse iron oxide nanoparticles with an average particle size ranging from 5 to 43 nm were fabricated using an environmentally friendly starting material, ferrous acetate. The smallest particles were formed in the presence of a reductant, 1,2-dodecanediol, while the particle size increased with increasing concentration of dispersing agents. The dispersants consisted of various combinations of oleic acid, oleylamine, trioctylphosphine, and polyvinylpyrrolidone. The threshold temperature to form crystalline particles was found to be $240^{\circ}C$. The 43 nm nanoparticles exhibited a room temperature saturation magnetization and coercivity of 57 emu/g and 47 Oe, respectively.

• Macromolecular Research
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• v.15 no.5
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• pp.403-411
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• 2007

Monodisperse micron-sized polystyrene (PS) spheres were successfully obtained using a single stage soap-free emulsion method in aqueous media mixed with ethanol (co-solvent) containing NaCI as the electrolyte. The optimum conditions for preparing the monodisperse PS microspheres, using soap-free emulsion polymerization in a water/ethanol mixture with an electrolyte, were studied. The presence of the co-solvent and electrolyte controlled the particle dispersion stability during the polymerization. The microspheres formed using PS, with a weight-average diameter of $2.6{\mu}m$, coefficient of variation of 5.3% and zeta potential of -15.1 eV, were successfully obtained in the presence of 0.1 wt% NaCI, 10 wt% monomer, 0.1 wt% initiator and 95/5 (g/g) of a water/ethanol mixture reacted at $70^{\circ}C$ for 24 h.

• Macromolecular Research
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• v.15 no.3
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• pp.244-255
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• 2007

Nucleation is the most sensitive stage in the preparation of highly cross-linked, monodisperse microspheres by dispersion polymerization, since the addition of a small amount of cross-linker results in particle deformation and coagulation. To overcome these problems, $5\;{\mu}m$ poly(methyl methacrylate) seed particles prepared by dispersion polymerization were used in the preparation of mono disperse, cross-linked PMMA particles containing up to 7 wt% divinylbenzene by seeded batch dispersion polymerization. Spherical particles with a narrow size distribution containing up to 8 wt% of EGDMA were prepared by seeded multi-batch dispersion polymerization processes. These particles were identified by scanning electron microscopy and DSC.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.792-799
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• 2016

Monodisperse silica nanospheres were synthesized by Stober method using rotating cylinder systems with batch or continuous manner. The particle size could be controlled by adjusting the reactant compositions such as the amount of monomer, catalyst, and water in the reaction mixture. The size and monodispersity of the ceramic particles could be controlled by changing the reaction medium with different alcohols other than ethanol or changing the reaction temperature. The effect of Taylor number (Ta) on the average diameter and standard deviation of silica particles were also studied by adjusting the rotation speed of inner cylinder, and the maximum diameter of particles was observed at Ta ${\approx}3,000$.

• Journal of the Korean Ceramic Society
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• v.46 no.5
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• pp.472-477
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• 2009

Monodisperse spherical $SiO_2$ particles of various sizes ($\sim$350 nm and $\sim$800 nm) and size distributions were synthesized from TEOS and MTMS. The particle size and size distribution were controlled by changing the volume ratio of water to ethanol and the reaction temperature. Narrow-sized $SiO_2$ particles with $\sim$3% size distribution were obtained. Self-assembly of the $SiO_2$ particles for photonic crystals were performed by the solvent evaporation method. The number of ordered $SiO_2$ layers can be controlled by changing the amount of the dispersed $SiO_2$ volume fraction in the solvent.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2002.11a
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• pp.112-114
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• 2002

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.9
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• pp.1175-1182
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• 2001

Chemical compositions of polydisperse SiO$_2$/TiO$_2$multicomponent aggregates were measured for different heights from the burner surface and different mobility diameters of aggregates. SiO$_2$/TiO$_2$multicomponent particles were generated in a hydrogen/oxygen coflow diffusion flame from two sets of precursors: TTIP(titanium tetraisopropoxide), TEOS(tetraethylorthosilicate). To maintain 1:1 mole ratio of TTIP:TEOS vapor, flow rate of carrier gas $N_2$was fixed at 0.6lpm for TTIP, at 0.1lpm for TEOS. In-situ sampling probe was used to supply particles into DMA(differential mobility analyzer) which was calibrated with using commercial DMA(TSI, model 3071A) and classifying monodisperse multicomponent particles. Classified monodisperse particles were collected with electrophoretic collector. The distributions of composition from particles to particle were determined using EDS(energy dispersive spectrometry) coupled with TEM(transmission electron microscope). The chemical(atomic) compositions of classified monodisperse particle were obtained for different heights; z=40mm, 60mm, 80mm. The results suggested that the chemical(atomic) composition of SiO$_2$decreased with the height from burner surface and the composition of SiO$_2$and TiO$_2$approached to the value of 1 to 1 fat downstream. It is also found that the composition of SiO$_2$decreases as the mobility diameter of aggregate increases.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.6
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• pp.2005-2013
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• 1996

Particle paths and flow fields in a prototype differential mobility analyzer (DMA) were numerically analyzed solving Navier-Stokes equation, electric field equation and particle motion considering viscous drag force, Coulomb force and polarization force. Analytically predicted particle diameters for the prototype DMA are in good agreement with the measured particle diameters within $\pm$1%. And the analytically predicted particle diameters are also in good agreement with numerical results for the prototype DMA.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.7
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• pp.741-746
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• 2004

Agglomerated and non-agglomerated SiO$_2$ particles are synthesized in a furnace by oxidation of TEOS vapor. These polydispersed particles are classified with DMA to extract particles. Then these particles are introduced into a thermal precipitator through the ESP(Electrostatic Precipitator) to investigate the themophoretic particle deposition using CNCs(Condensation Nuclei Counter). The efficiency of themophoretic particle deposition according to agglomerated and non-agglomerated particles in the thermal precipitator has been studied as a function of particle size and TEOS mole concentration using monodisperse particles classified by DMA. The results show that the particle deposition efficiency decreases as TEOS mole concentration increases and particle size increases. Thereffre, it is concluded that the thermophoretic deposition efficiency is dependent of the particle morphology.

• Membrane Journal
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• v.29 no.1
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• pp.61-65
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• 2019

Anisotropic particles have been issued in various fields due to their unique physical properties. Herein, a novel dynamic phase separation method (DPS) is introduced to fabricate anisotropic acorn-like nanoparticles. DPS consists of two dynamic conditions; solvent evaporation and nonsolvent induced precipitation. The bottom layer is controlled by feeding the water as a non-solvent diluent, and the phase separation of the upper layer relies on the diffusion and evaporation of a volatile good solvent. At this condition, the acorn-like particles were fabricated. Under a closed box filled with water (spontaneous phase separation), monodisperse polystyrene (PS) particles were synthesized. At the coexistence between DPS and spontaneous phase separation, the sizes of cap and particle were changed. Also, the volume of PS solutions influences on the particle shape. Since the unique structures could be utilized into various applications, if advanced techniques such as membrane-based controlled water feeding is developed, monodisperse acorn-like particles could be tuned.